Field application of thermosetting resin

ABSTRACT

A method for on-site building construction using thermosetting resin and means for electrically setting the resin substantially instantaneously to provide structurally sound joints is disclosed. The method permits the use of thermosetting resins under adverse conditions of temperature and environment.

United States Patent Joiner, Jr.

1 51 3,707,062 Dec.26,1972

[54] FIELD APPLICATION OF THERMOSETTING RESIN [72] Inventor: FleetwoodB. Joiner, Jr., 703 North Bayfront, Balboa Island, Calif. 92662 [22]Filed: Feb. 2, 1970 [21] Appl. No.: 7,954

52 US. (:1. ..52/741,52/173,52/309, 287/189.36 A 511 1111. C1 ..E04bl/58, E04b 1/60 [58] Field 61 Search ..52/127, 173, 309, 741; 264/27;287/189.36 A

[56] References Cited UNITED STATES PATENTS 1,460,941 7/1923 Broughton..52/495 X 1,678,504 7/1928 Glover ..52/495 X 2,378,801 6/1945 Sidell etal. ..52/309 X 2,497,657 2/1950 Cole ..46 31 3,111,569 11/1963Rubenstein... ..s2/232 x 3,258,888 7/1966 Lum ..s2/309 x 3,263,2688/1966 Flaherty ..264 27 3,415,028 12/1968 Nerem ..52/309 x 3,492,3811/1970 Rhyne ..264/27 FOREIGN PATENTS OR APPLlCATlONS 680,240 2/1964Canada .52 309 605,964 8/1948 Great Britain ..287/189.36 A

Primary Examiner-Alfred C. Perham Attorney-Fowler, Knobbe & Martens [57]ABSTRACT A method for on-site building construction usingthermosetting-resin and means for electrically setting the resinsubstantially instantaneously to provide structurally sound joints isdisclosed. The method permits the use of thermosetting resins underadverse conditions of temperature and environment.

2 Claims, 7 Drawing Figures PATENTED m2 3.707.062

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' FIELD APPLICATION OF THERMOSETTING RESIN RELATED APPLICATIONApplication Ser. No. 881,949 filed Dec. 4, 1969, for BUILDINGCONSTRUCTION UTILIZING PINNED PANELS, by Fleetwood B. Joiner.

This invention relates to the construction of static structures such asdwelling houses, industrial and commercial buildings. The inventionrelates in a more specific manner to a method for on-site constructionof load bearing structural components of buildings using thermosettingresin.

Glues of various types, including thermosetting resins, have gained wideacceptance in the fabrication of components and assemblies wherestructural strength is of secondary importance or the resin can bemaintained under controlled conditions of temperature and environmentduring hardening or setting. Thermoplastic and fusible materials havebeen used in a variety of applications to form seals. Thermoplasticmaterials generally have insufficient bonding strength for use in loadbearing constructions or where structural strength requirements aresignificant. Thermoplastic and thermosetting materials have heretoforebeen unsuitable for use in on site construction of buildings and, inspite of the advantages thermoplastics possess in terms of flexibility,pre-formability, etc., neither thermosetting nor thermoplastic resinsmeet building code requirements for load bearing structural units.

The bonding strength of thermosetting resins generally and particularlyof epoxy resins, certain polyester resins, etc., have been recognizedand such thermosetting resins can be used in the prefabrication ofcertain modules or other structural units for subsequent use in theconstruction of a building, under circumstances such that-the settingconditions for the resin can be controlled. Field applied thermosettingresins, however, are unacceptable under building codes for the bondingload bearing units of a building. The use of thermosetting resins in areinforcing member, such as a cable, to rigidify the reinforcing memberin which the resin is set by electrically applied heat has been proposedbut the prior art presents no satisfactory -means or methods forovercoming the difficulties in and obstacles to the use of thermosettingresins in onsite building construction.

A method is provided, according to the process of this invention,whereby the convenience and economic advantages of field application ofadhesively bonded joints are obtainable. Such advantages could notheretofore be obtained because adhesive joints formed in the field werenot acceptable under building codes, since such joints could not berelied upon to have the necessary bonding strength.

According to this invention, a building is constructed by arrangingbuilding units in the configuration of at least a part of the buildingsuch that edges of the building units are adjacent to each other. Theseedges are then joined using the novel techniques described herein. Thesetechniques include the placing of a layer of thermosetting resinadhesive between the edges of the building units, placing an electricalconductor along the layer of resin such that heat produced by theconductor is applied to the resin, and producing an 0 mosetting resinspractical in the field construction of buildings, a result which couldnot heretofore be accornplished. I

The electrical conductor can be placed along the resin to provideelectrically produced heat in the resin in a number of ways. The mostdirect method for placing the conductor in heat conductive relation withthe resin is to embed one or more electric wires along the adhesivelayer in contact with the resin. Electricity is then applied to the wireto produce the necessary heat in the adhesive joint to set thethermosetting resin quickly and reliably.

According to one particular feature of the invention, the step ofplacing the electrical conductor along the resin layer comprises theinclusion of at least one electrically conductive building unit as apart of the joint. to be formed. This is advantageous in certainbuilding constructions in that it avoids the necessity for theadditional step of placing a wire along the adhesive joint.-

According to another particularly advantageous feature of the invention,the placing .of the electrical c'onductor along the resin layercomprises the step of including a material in the resin which makes theadhesive layer electrically conductive. Electricity is then simplyapplied to the adhesive layer to produce the heat necessary to setthe'resin substantially instantaneously. Heat may be electricallyproduced in the resin by direct connection of the electrical conductorto a source of direct or alternating current 'or by inducing electricityinto the conductor indirectly.

Building codes generally forbid the use of adhesive resins in on-sitebuilding construction. This rule .is relaxed in certain instances wherethe entire glue line is visible and available for inspection. The use ofresin bonded elements in structural units, however, has not beenfeasible where the structural units are required to bear substantialloads. According to a principle feature of this invention, thesedisadvantages are overcome and on-site use of adhesive resins in loadbearing structural units is made possible.

According to one feature of thisv invention, a complete or substantiallycomplete building may be assembled by the arrangement of building units,the joints being initially formed by placing a layer of resin adhesivebetween the edges of the various building units. When the building issubstantially completely assembled, using temporary bracing ifnecessary, then electricity is applied to the adhesive joints throughoutthe entire building simultaneously, or to the various major elements ofthe building individually, to set the resin substantiallyinstantaneously. By careful placement of the conductors, and applicationof the electrically produced heat to the resin, an entire building canbe bonded to form one integral load bearing structure. This buildingtechnique is especially applicable to the construction of buildingsaccording to the principles set forth in my copending application Ser.No. 881,949,

or bolt steel structural members together in a construction of abuilding in the field. This is time consuming and expensive. Accordingto one of the features of thisinvention, structural steel or otherstructural metal units are bonded together by the substantiallyinstantaneous setting of thermosetting resin adhesives.

The various advantages and features of the invention are similarlyapplicable to building structures which are constructed in part of steelor other metal building elements.

These and other features will become apparent from the specificationwhich follows and from the drawing to which reference is made, it beingunderstood that the drawings and illustrations are intended only toexemplify the invention and not to limit the applicability of thestructures, methods and techniques described herein.

FIG. 1 is a perspective view showing the application of the inventiveprocess to the construction of an integrally bonded building using theprinciples described and claimed in my aforesaid copending patentapplicatron.

FIG. 2 is an enlarged view showing one method for forming the adhesivejoint of this invention.

FIG. 3 illustrates an alternative method for forming the adhesive jointof this invention.

FIG. 4 is a perspective view of a corner joint formed according to theprinciples of this invention and FIG. 5 is a horizontal section of thecorner joint illustrated in FIG. 4 taken substantially along lines 55 ofFIG. 4.

FIG. 6 is a perspective view of a joint formed of structural steel usingthe techniques of this invention and FIG. 7 is a vertical section of thejoint illustrated in FIG. 6 taken substantially along lines 7-7 of FIG.6.

Reference is made to FIG. 1 which illustrates a preferred and especiallyadvantageous application of the method of this invention. According tothis feature and application of the invention, a building is constructedusing the techniques and concepts described in my aforesaid copendingpatent application and the method for forming joints which constitutes aprincipal feature of this invention. a

An integrally bonded building, part of which is shown at 10, isconstructed using the elements described in my copending patentapplication and illustrated in abbreviated form in FIG. 1. The floor ofthe building 12 may be formed, for example, of a plurality of floorpanel units 14, 14a, 14b, ,etc. The load bearing walls 16 areconstructed according to this feature of the invention utilizing pinnedpanels as more fully described and claimed in my aforesaid copendingpatent application.

Reference is made to said patent application for a complete discussionof the concepts and constructions involving the utilization of pinnedpanels for building constructions. Briefly, however, a building isconstructed according to the principles set forth in my aforesaid patentapplication by constructing load bearing walls from panels which are socomposed and constructed as alone to be incapable of supporting anysubstantial vertical load, such as imposed by a permanent roof, secondstory, etc. These normally non-load bearing panels are pinned for at.least three-fifths their height. The pinning may be accomplished by likeor similar panels joined to form corners such as illustrated at 18, 20,22, 24, and 26 in FIG. 1. These corners may be single corners as shownat 18, for example, or double comers as shown at 20, for example. Agreat many corner configurations are, of course, possible withoutdeparting from the scope of the inventive concept. The panels may alsobe pinned by using vertical shaft elements which may be in the form ofnon-load bearing pins secured along the vertical edge of a panel, ordoor or window jambs, etc. The pinning elements should encompass atleast the center three-fifths of the height of the panelto be pinned.The reader is referred to my copending patent application for a completediscussion of the concepts and advantages of building construction usingpinned panels. 4

The roof 32 of the building may be of any desired construction but,according to the present invention, is advantageously composed of aplurality of roof panels 34, 36, etc.

The pinned panel units, along with other building elements, areassembled in the configuration of a complete or substantially completebuilding or building module, the edges of the building units beingjoined with a thermosetting resin adhesive. If temperature and otherenvironmental conditions were ideal, the building could be assembled asdescribed and simply maintained in the proper configuration duringnormal setting of the resin. Even under ideal conditions, however, thistechnique of building construction suffers from certain very seriousdrawbacks.

For example, serious difficulties may be faced even if the building isto be constructed on-site on a hot, dry summer day, these conditionsbeing desirable to form a strong thermoset adhesive bond. If thethermosetting resin used as the joining adhesive is formulated to have ashort pot life, then the resin will begin setting as each individualjoint is formed and during the formation of subsequent joints thepreviously formed resin joints will be disturbed. The disturbance of apartially set resin joint is likely to result in a completely set resinadhesive joint which is not structurally sound and may not even beweather tight.

On the other hand, if the thermosetting resin is compounded to have along pot life, the building can be assembled substantially completelybefore any significant setting of the resin begins. In this case,however, the conditions necessary for satisfactory setting of the resinare not likely to prevail for a sufficiently long time to form bondedjoints having adequate structural strength so as to form a load bearingbuilding or building module.

These disadvantages are overcome according to the present invention byplacing an electrical conductor along the adhesive layers. In theembodiment illustrated in FIG. 1, electrical conductors 38, 40, 42 and44, which may be wires or cables, are placed along the top and bottomsof the walls in one direction. Similar conductors, exemplified at 46 and48, are placed along the tops and bottoms of the walls in the otherdirection and a conductor 50 may be placed along the roof line of thebuilding. Electricity may be applied from a single source or from aplurality of isolated sources as indicated by the polarity illustratedin FIG. 1.

By appropriate connection of the conductors to a single source or toplural isolated sources, the entire building, or building module can becompletely or substantially assembled using a thermosetting resin ofadequate pot life. Once the building is assembled, electricity isapplied to all of the conductors. This simultaneously sets-all or atleast a majority of the structural joints in the building to form anintegral load bearing structure. Such a structure has greater strength,load bearing capacity and rigidity than a similar structure in which theindividual building units are joined separately.

It is pointed out that the placement of the conductors in the embodimentillustrated in FIG. 1 is merely illustrative of the placement ofconductors along adhesive layerjoints and is not intended as anexhaustive illustration of the placement of all conductors in abuilding. Obviously, the placement of conductors in a given buildingwill depend upon the number of load bearing walls and relative placementof the load bearing walls in the building. Non-load bearing walls may bejoined according to the techniques of this invention also, but non-loadbearing wall joints can satisfactorily be formed using thermosettingresins without the need of the instantaneous setting techniquesdescribed herein.

FIG. 2 illustrates in greater detail the construction of building jointsaccording to this invention and the process for forming such joints.This exemplary building joint may be in a building of the typeconstructed according to the process described in my aforesaid copendingpatent application, although I do not limit my invention to theformation of joints in that type of building.

A panel 52 may, for example, be joined along a vertical edge 54, a topedge 56 and a bottom edge 58. The vertical edge is joined to a pinningmember, another panel, or another vertical element of any desired typeor configuration. The top edge is joined to a plate 60 which, in theillustrative embodiment, is morticed to receive the top edge of thepanel. The bottom edge is joined to a floor 62.

According to the process of this invention, an adhesive layer 64 isplaced along the vertical edge 54 of the panel 52, and,similarly,-adhesive layer 66 is placed along the top edge 56 andadhesive layer 68 is placed along the bottom edge 58 of the panel 52.Conductor 70 is placed along the adhesive layer 66 and conductor 72 isplaced along the adhesive layer 68. A separate conductor may be placedalong the adhesive layer 64 as well but, as will be discussed, this isusually not necessary.

Once the edges of the building elements are joined with the adhesivelayer, then electric energy is applied to the conductors 70 and 72. Thiselectrically heats the adhesive resin layers 66 and 68 to formsubstantially instantaneously a thermoset cured adhesive bond betweenthe panel edges and the adjacent edges of the other building units. Thissetting of the resin layers 66 and 68 begins the polymerization processwhich tends to follow up the adhesive layer 64 from the bottom layer 68and down the adhesive layer 64 from the top layer 66. Thus,instantaneous thermosetting of resin layer 64 is accomplished eventhough-no conductor is directly in contact therewith. Even if thevertical joint resin layer 64 is very long, the ends of the verticaljoint can be set thus fixing the relative positions of the verticalmembers to permit completion of the setting of the vertical joint.Additional setting of the vertical joint can be accomplished by themethod illustrated in FIG. 3, if required.

Depending upon the particular building being constructed, the techniqueas just described may be satisfactory. However, for relatively longlengths of resin, setting of the resin layer 64 may require that anadditional conductor be placed as previously described. Complete settingof this resin may also be accomplished by associating a conductor withthis adhesive layer by adding a material to the resin during compoundingto make the resin electrically conductive. By appropriate polarityapplication, electricityis conducted from the conductor to the conductor72 through the adhesive layer, thereby substantially instantaneouslysetting the resin in layer 64. The layers 66 and 68 may also be madeelectrically conductive this way in lieu of or in addition to theplacing of the conductor 70 and 72 therealong.

An alternative method for producing an electric current in the conductoris illustrated in FIG. 3 in which a panel 74 is joined to a panel 76 bya thermosetting adhesive resin layer 78 which, in a preferred embodimentmay include metal flakes or powder, aluminum fillers, for example, torender the adhesive conductive. The panels may be bonded in like mannerto the plate 80. According to this embodiment of the invention anelectrical induction device 82 is passed along the joint to electricallyinduce current in the conductor in the resin. Actually, the sametechnique may be used to induce electricity in a conductor such as awire or a plurality of wires which are laid along the layer of adhesivebut since this method of producing electricity in the conductor issomewhat less efficient than direct application of electrical voltage tothe conductor, the latter technique is preferred.

Induction heating of conductors is a well known technique and the readeris referred to electrical engineering texts and the electricalengineering art generally for a discussion of the equipment and thetechniques used in the application of this process. Generally speaking,sufficient heating of the conductor associated with the adhesive resincan be accomplished using frequencies from 60 to 600 cycles per secondalthough frequencies from 60 cycles per second to 1,000 kilocycles orhigher may be used effectively. Optimum frequency will depend upon thetype of conductor used and the thickness of the joint being formed. Theinductor device 82 includes an induction coil. The flow of current inthe coil produces a magnetic field or flux which surrounds each turn ofthe coil. This flux passes through the air and through any conductorthat is near the coil. Each reversal or alternation of the currentcauses the flux in the conductor to change. The change of flux induces avoltage in the conductor which forces large eddy currents to flowthrough the conductor. These induced currents produce heat in theconductor which sets the resin.

It is also possible to set the resin in a joint, for example adhesivelayer 78, without the inclusion of a conductor by the use of dielectricheating. Dielectric heat transfer is somewhat less efficient than themethods of heating previously described and the equipment for producingdielectric heat is expensive and complex. The previous techniques are,therefore, preferred but if non-conductive resin is preferred orrequired in a particular installation, dielectric heating of the resinlayer is highly advantageous in that it assures a substantiallyinstantaneous set of the resin thus assuring a strong structuralbond.Dielectric heating requires frequencies from about I megacycle to 50megacycles or higher. The very rapid reversal of the electric fieldsurrounding the dielectric heater distorts and agitates the molecularstructure of the resin such that internal molecular friction generatesheat uniformly through all parts, of the resin thereby causing thethermosetting resin to set. Again, the reader is referred to theelectrical engineering art for details concerning the equipment suitablefor dielectric heating. Specific reference is made to Chute, ELECTRONICSIN INDUSTRY, Second Edition, McGraw-I-Iill, I956, and the referencescited therein.

In the embodiments discussed hereinbefore, an electrical conductor wasplaced in association with the adhesive layer for the sole purpose ofelectrically heating the layer to set the resin. FIGS. 4 and 5illustrate in simplified form the utilization of the techniques of thisinvention wherein electrically conductive structural components areutilized as conductors for setting the resin in the formation of theadhesive bond. In the illustrative embodiment of FIGS. 4 and 5, threepanels 84, 86 and 88 are arranged with their edges adjacent each other.A layer of adhesive, indicated generally at 90 of suitable configurationis placed along the edges of the panels. An electrically conductivemolding 92 and 94 is placed at the intersection of the panels. Themolding in this illustration is shown as an angle member which may becomposed of iron, aluminum, magnesium, or any other conductive material.It may, forexample, be made of a decorative polymer which has aluminum,brass, or other metal flake therein to make the molding at leastsemi-conductive. The molding may, of course, be in any desiredconfiguration. Once the panels and molding are in the proper arrangementrelative to each other, electric energy is applied to the moldings toelectrically heat the resin adjacent thereto. a

The panels may be conductive but also may be nonconductive panels suchas plywood, fiberboard, or a composite of building materials. In oneembodiment of the invention, the resin -is made partially conductive,for example, by the inclusion of flake aluminum in the resin duringcompounding, and electricity is caused to flow from the molding 90through the resin to the molding 94 for producing a bonded thermosetadhesive resin joint.

Adhesively bonded joints of this type are quite suitable for theformation of load bearing walls and other structures in a building.Thermosetting resins applied according to the techniques of the priorart could under ideal temperature and atmospheric conditions form loadbearing structurally sound joints but the builder could not rely uponthe formation of structurally sound thermoset resin joints and the onlyway to determine whether the joint was sufficiently bonded was, ineffect, to destroy the very joint which was to be tested.

FIGS. 6 and 7 illustrate a further application of the broad concept ofthis invention. In this application, a joint indicated generally at of,for example, vertical I-beams 102 and 104 and horizontal I-beams 106 and108 is formed of a single unitary resin bond indicated generally at 110.In addition to the I-beam elements of the joint, angle braces 112 and114 strengthen-the joint between the I-beam 104 and l-beams 106 and 108and angle braces-116 and 118 likewise strengthen the joint betweenI-beam 102 and l-beams 106 and 108. A scab 120, on one side of l-beams106 and 108 and a like scab on the other side may also be included toprovide additional strength to the joint.

In the embodiment of the invention illustrated, an adhesive layer isplaced between the edges and/or faces of the elements of the joint to bebonded.

together. In the particular joint illustrated, the adhesive layer iscontinuous and follows the general configuration of the intersectingelements but this is not necessary to the invention. Once the elementsof the joint are in place and the adhesive layer has been placedtherebetween, then electricity is applied to the respective I-beams, forexample. Electricity may be applied,

,for example, between I-beams 106 and 108 and/or between I-beams 102 and104 to provide electrical heating of the intersection. Thissubstantially instantaneously sets the resin forminga structurally soundadhesive bond. This permits the assembly of the joint using the liquidresin and setting of the resin in one relatively simple step. Thispermits easier alignment of the elements, forms a joint 4 ofexceptionally high strength and is less expensive and more efficientthan the techniques of the prior art. v

An I-beam joint is illustrated but, of course, structural metal elementsof steel, aluminum, etc. of any desired configuration may be bondedutilizing the methods and techniques of the invention as described.

FIG. 7 illustrates one application of the method and structural systemof this invention. According to this feature of the invention, thestructural elements are provided with mating dowels and apertures, shownat 122 and 124, which add to the structural strength and rigidity of thebuilding unit. The dowels are received in corresponding apertures andbonded therein by means of the resin layer 110, when the resin layer isset by the application of electricity.

The term instantaneous setting, and variations thereof, as used hereinmeans the very rapid setting of the resin under the influence ofrelatively high temperatures producible only by application ofartificial heat to the resin. The actual setting time is a function ofthe resin type and, more directly, of the particular resin formulation.Setting times, as contemplated in this invention may be as little asseveral seconds to as long as several minutes, both times being muchshorter than to thermosetting adhesives. Phenolic resins, phenolformaldehyde, for example, and urea formaldehyde resins may be usedaccording to the present invention but by far the most useful and mostadvantageous class of thermosetting resin adhesives are the epoxyresins. Epoxy resins are characterized by having reactive oxirane ringsin the resin structure. They are commonly supplied in both, liquid andsolid form. In use, these epoxides are either homopolymerized with theaid of catalysts or copolymerized with hardeners such as polyamines,polyamides and anhydrides. Epoxy resins can be formulated having veryshort or relatively long pot lives and may include fillers andextenders, some of which may be conductive so as to form-a conductor inassociation with the resin layer. Epoxy resins are well known and thetechniques for manufacturing and handling these resins to achieve thedesired strength, adhesive, and pot lifecharacteristics are well knownin the polymerization art.

Certain cross-linked polyesters form adhesive resin joints ofsatisfactory strength and may be set using the techniques of thisinvention. Curing, of the polyester resin is initiated by the additionof a catalyst along with activators to promote the cross-linkingreaction such that the cure can be effected by the application of hightemperatures for comparatively short times. Cobalt naphthanate is acommon promoter but many other promoters and catalysts are available.Inhibitors may be added to the resin formulation to provide initialresin stability and, along with the catalysts, promoters, etc. toregulate the pot life and set time for cure. The considerations areknown to those skilled in the polymerization art and no extendeddiscussion is warranted. The reader is referred to the polymerizationart generally for the practical and theoretical considerations involvedin selecting appropriate thermosetting resins and to the particularmanufacturers use manuals and instructions for detailed informationrelative to the use of a particular resin. Thermosetting resins of thistype are commercially available from many suppliers.

The use of thermosetting resins in on-site building construction in thefield, using the techniques of this invention, results in buildingconstructions and buildings involving the novel combination of buildingunits, adhesive layers and conductors. These techniques provide meansfor using thermosetting resins in an environment and application whichhas not heretofore been possible. Moreover, the buildings constructedaccording to the principles of this invention possess greater strengthand rigidity than buildings constructed according to the principles andpractices of the prior art. In addition to these advantages andimprovements in the building structure, as compared with the prior art,the techniques of the process described herein permit more economicalconstruction of residential, business and commercial buildings.

As previously pointed out, the techniques of this invention find thegreatest economical advantage in the construction of buildings accordingto the techniques and principles described and claimed in my aforesaidpatent application using pinned panels, but the techniques of thisinvention are not limited to the construction of such buildings and,likewise, are not limited to the specific embodiment as disclosedherein.

Modifications and adaptations of the techniques discussed and thestructures discussed and illustrated maybe made by those skilled in theart based upon the teachings herein without departing from the spiritand scope of the claims which follow.

What is claimed is:

l. The method of bonding load-bearing metal structural building elementstogether which comprises joining said elements with a layer ofthermosetting resin adhesive at the building site under fieldenvironmental conditions and electrically heating said metal to therebyheat resin to substantially instantaneously set said resin to form anintegrally bonded joint between said building elements.

2. The method as described in claim 1 wherein the building elementscomprise mating dowel pins and apertures, the dowel pins being securedin the apertures by the resin adhesive upon electrical heating.

2. The method as described in claim 1 wherein the building elementscomprise mating dowel pins and apertures, the dowel pins being securedin the apertures by the resin adhesive upon electrical heating.